Water reaches Mars' upper atmosphere Mars once hosted abundant water on its surface but subsequently lost most of it to space. Small amounts of water vapor are still present in the atmosphere, which can escape if they reach sufficiently high altitudes. Fedorova et al. used data from the ExoMars Trace Gas Orbiter spacecraft to determine the distribution of water in Mars' atmosphere and investigate how it varies over seasons. Water vapor is sometimes heavily saturated, and its distribution is affected by the planet's large dust storms. Water can efficiently reach the upper atmosphere when Mars is in the warmest part of its orbit, and this behavior may have controlled the overall rate at which Mars lost its water. Science, this issue p. 297 ExoMars Trace Gas Orbiter data show how the distribution of water vapor in the atmosphere of Mars varies with the seasons. The loss of water from Mars to space is thought to result from the transport of water to the upper atmosphere, where it is dissociated to hydrogen and escapes the planet. Recent observations have suggested large, rapid seasonal intrusions of water into the upper atmosphere, boosting the hydrogen abundance. We use the Atmospheric Chemistry Suite on the ExoMars Trace Gas Orbiter to characterize the water distribution by altitude. Water profiles during the 2018–2019 southern spring and summer stormy seasons show that high-altitude water is preferentially supplied close to perihelion, and supersaturation occurs even when clouds are present. This implies that the potential for water to escape from Mars is higher than previously thought.

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火星上的暴风雨：沙尘季节大气水的分布和饱和度

水到达火星的高层大气 火星表面曾经拥有丰富的水，但随后大部分都流失到了太空。大气中仍然存在少量水蒸气，如果它们达到足够高的高度，它们就会逸出。费多罗娃等人。使用 ExoMars Trace Gas Orbiter 航天器的数据来确定火星大气中水的分布，并研究它如何随季节变化。水蒸气有时会严重饱和，其分布受到地球大沙尘暴的影响。当火星处于其轨道最温暖的部分时，水可以有效地到达高层大气，这种行为可能控制了火星失水的总体速度。科学，这个问题 p。297 ExoMars 微量气体轨道飞行器的数据显示了火星大气中水蒸气的分布如何随季节变化。从火星到太空的水流失被认为是由于水被输送到高层大气，在那里它被分解为氢并逃离地球。最近的观察表明，水大量、快速地季节性侵入高层大气，增加了氢的丰度。我们使用 ExoMars 痕量气体轨道飞行器上的大气化学套件来表征按高度划分的水分布。2018-2019 年南部春季和夏季风暴季节期间的水剖面显示，高海拔水优先供应接近近日点，即使存在云也发生过饱和。